This is a test

# Equations for the Final

I am going to give you the following equations on the final exam. # Stuff for final

So, for the final exam, here is stuff that was not covered on the last test:

- What makes an electric circuit
- What is current
- How do you light a light bulb
- Energy transfers and changes in a circuit
- Electric forces
- Electric charges
- Electric charges in matter
- transfer of charges
- polarization
- electric potential
- changes in electric and magnetic fields (induction)
- production of electromagnetic fields
- generators and motors

# Light simulator

I am going to use this simulator in class: # Balloon simulation

Here is the simulator for the balloon thingy. # fix for building a circuit

I uploaded the presentation on what makes a circuit to blackboard. Sorry for the mistake.

# Test 4 key

1. Describe the difference between the wavelength and frequency of a wave.

Wavelength is the distance from one peak of a wave to the next. It is measured in meters. Frequency is how many peaks pass a stationary point in one second. This is measured in Hertz.

What is the difference between x-rays and visible light?

The only real difference between these two waves is the wavelength and frequency. They are both electromagnetic waves. Of course, this means that they interact differently with matter.

Which has the longest wavelength: visible light, ultraviolet, or radio waves? Which travels with the fastest speed?

Radio waves have the longest wavelength. All EM waves travel at the same speed.

Before the discovery of the electron, the accepted model of the atom was that it was a single particle. After the discovery of the electron, how did Thomson change the model of the atom? (Describe Thomson’s model of the atom).

Thomson’s model of the atom had electrons embedded in positive “stuff”. This is often called the plum pudding model where the electrons are the plums.

Describe one important difference between Bohr’s model of the atom and Rutherford’s model of the atom.

Both models had a positive nucleus, but in Bohr’s model, the electrons could only exist at certain energy levels.

When an object increases in temperature, what are two things that change about the radiation it gives off?

As an object increase in temperature, it gives off MORE radiation and the peak wavelength of radiation produced gets shorter.

How does the greenhouse effect work?

In the greenhouse effect, visible light from the Sun goes through the atmosphere and warms the ground. This warm ground emits infra red radiation. This IR radiation does NOT go through the atmosphere and instead warms the atmosphere.

Water is made of hydrogen and oxygen. When liquid water boils, tiny bubbles of gas are formed. What is this gas?

The gas is water vapor.

Give an example of an element. Give an example of a compound.

An element just has one type of atom in it. An example is helium gas. A compound has more than one type of element. Example: water.

If you wrap a wool blanket around a thermometer, what happens to the reading of the thermometer? Why?

Nothing happens to the reading of the thermometer. The blanket and the thermometer are at the same temperature, so no energy is transferred between the two to cause a change in temperature.

Suppose you turn on a stove burner till it is hot and then turn it off. After the burner is off, you put your hand near it. What happens to the thermal energy in your hand and in the burner?

The stove burner cools off and decreases in thermal energy. Heat is transferred to the hand. The hand warms up and increases in thermal energy.

A friend says that in a mixture of gases in thermal equilibrium, the molecules have the same average speed. Do you agree or disagree? Why?

If the gases are in thermal equilibrium, they would have the same kinetic energy. However, if the two gases have different masses, they can have different speeds with the same kinetic energy.

Can light travel through a vacuum? What evidence do you have that supports your answer.

Yes. Light travels from the Sun to the Earth in a vacuum.

# Test 4 stuff

So, I didn’t really get far into chapter 8 today in class. The only thing we really went over was more about heat conduction interaction and IR interactions. This was essentially review of previous material. Chapter 8 will not be on test 4.

# extra homework

Since I am using some stuff that is not from the book - I have put some extra homework assignments in blackoard that should help.

# Chapter 7 homework

Here are some homework problems:

Chapter 7
Review questions: 5, 9, 11
Exercises: 1, 9, 10,

Chapter 10
Review questions: 1, 4, 5
Exercises: 2, 3, 7, 17

Chapter 11
Review questions: 1, 2, 3, 4
Exercises: 1, 5, 8, 10

Chapter 12
Review questions: 4, 5, 21
Exercises: 21, 22, 23,

# Chapter 8

I made some changes to chapter 8. On blackboard, there are two presentations. The first one is basically stuff from the book. The second one is more interactive stuff that we will do in class.

# atomic simulators

Here are some cool simulators:

Rutherford’s experiment: Several models: Another Bohr Model # Chapter 7

Sorry, but chapter 7 became kind of messy. I wanted to add some stuff to make everything fit together better. So, if you want to follow along with the lecture, here are the topics and chapter sections from the book:

Atoms - 12.1, 12.2, 12.3, 12.7, 12.8, 12.9
Waves - 10.1, 10.2
Doppler effect - 10.8
Light - 11.1, 11.2
Heat Stuff - 7.1, 7.2, 7.3, 7.4, 7.5

# Test 3

I know I am slow - but I finally posted Test 3 grades on blackboard. I hate blackboard. These are the unofficial grades as I could have made a entry error.

# Test 3 Key

My weight would be 700 Newtons. Weight is a gravitational force between me and the Earth. Neither of these things really changed, so the weight would be the same.

In this case, I am accelerating down. This means that the net force should be down. Since gravity doesn’t change, this means that the scale would push up less than 700 Newtons and it would read a value smaller than 700 Newtons.

While in orbit, the astronauts have a gravitational force only slightly smaller than they would on Earth. This is because they are a little bit farther away from the center of the Earth.

Both balls will hit the ground at the same time. They both start from the same height and both have the same initial vertical velocity. This means that their vertical motions will be the same.

Block A would have a density of 10/100 = 0.1 kg/cm^3. Block B would have a density of 1 kg/cm^3. Block B has a greater density. Block A has a greater volume because 100 is greater than 1.

The nails in all must exert a force up equal to the weight of the professor. Since there are 1000 nails, this gives some area. The pressure is F/A and this is not enough to puncture the skin. If there was only 1 nail, the pressure would be much higher (since the area is so small). This would produce a pressure great enough to puncture the skin.

The iron will have a greater buoyant force. Because it is completely submerged, it will displace more water. The buoyancy force is directly related to the amount of water displaced. The iron also has a greater weight.

You could say that thermal energy is the total amount of energy (due to the kinetic energy of the particles) in an object. Temperature is a measure of the average kinetic energy per particle.

Trucks have a very large weight. If they only had four tires, then they would have small surface area. With this the road would have to push up on the truck – that is fine. The problem is that with this surface area, there would be a huge pressure on the road – it would dent the road. With 18 wheels, the surface area is larger and the pressure smaller.

While the iron block is in the water, the water warms up. This means that its temperature and thus the average kinetic energy of the water particles increases. During this same time, the iron is losing energy. The average kinetic energy of the iron particles decreases.

What is this and what is it for?

When the bridge warms up, it expands. If this part was not here, the bridge would have no place to expand to and it would crack.

Since the sand both warms up very quickly and cools off quickly, it must have a low specific heat. If it had a high specific heat, it would take a lot of energy to increase the temperature.
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# Chapter 6 homework

Chapter 6 homework.

I was almost certain that I had posted this, but I don’t see it anymore. Here it is again:

Review questions: 2, 7, 8, 9, 25

Exercises: 7, 8, 25

# Stuff for Test 3

For the next test, you need to know:

Chapter 4:
- weight and weightlessness and apparent weight
- projectile motion
- orbital motion and satellites

Chapter 5:
- density
- pressure
- buoyancy
- pressure, volume and temperature in a gas (PV = NKT)
- Bernoulli’s principle
- The small particle model of gases

Chapter 6
- temperature
- thermal energy
- thermal expansion
- heat transfer

# suction dart in a vacuum

Here is a demo I made for you - this is that same dart I showed in class, but I put it in a chamber whereI pump out most of the air:

# Vacuum Spider Man

Here are the two videos I showed in class:

and here is part II

# Chapter 5 Homework

Review Questions: 3, 5, 6, 9, 13, 20

Exercises: 2, 7, 11, 12, 15, 17, 20, 37

# Stuff for Test 2

Reminder: Test 2 is on March 8 (as stated in the syllabus)

Test 2 will cover:

Chapter 3:
- Momentum Principle
- Work-Energy Principle
- Power
- Efficiency

Chapter 4:
- Newton’s Universal Law of Gravity

The test will be the same format as test 1. There will be no problems that require you to use a calculator - in fact, calculators are not allowed.

# Flip Flopper

I am the flip flopper. I am going to start putting presentations on BlackBoard instead of here. I will talk about this more in class.

# Something for Chapter 5

I know we haven’t even started chapter 4, but this is a great applet. I am going to use it for chapter 5. # Chapter 3 part 2

I am sorry. I said I would put up chapter 3 part 2 right after class and I forgot. Totally my fault.

It is up now.

# Chapter 4 HW

Review Questions:
3, 6, 8, 10, 12 16, 26

Exercises:
3, 6, 8, 10, 14, 17, 22, 26, 45

# Chapter 3 HW

Review Questions:
2, 4, 7, 11, 15, 20, 26

Exercises:
2, 4, 9, 11, 14, 24, 31

# Projectile Motion

Here is a projectile motion applet # Gravity Force

This will be useful for Chapter 4 - but I don’t want to forget about it.

Gravity Force calculations
http://phet.colorado.edu/simulations/sims.php?sim=Gravity_Force_Lab # Test 1 Key

Since it will be some time before we meet again, I am posting the key for Test 1 here.

1. If you kick a ball, it will roll and stop (assume it stays on the ground). Describe how both Aristotle and Galileo would explain why the ball stops.

Aristotle says (even though he is dead) that the ball will stop because there is no longer a force making it move.

Galileo says that the ball stops because there is a force making it slow down.

2. Suppose I throw a ball straight up with a velocity of +10 m/s. After 1 second, what is the velocity? After 1 second, what is the acceleration?

After 1 second, the velocity is 0 m/s and the acceleration is 10 m/s per second in the downward direction.

3. If the net force on an object is zero, what can you
absolutely say about that object?

If the net force is zero, then the object must be at a constant velocity. One possible case is a constant velocity at 0 m/s (which would be at rest).

4. A 10 Newton box is placed on top of a 5 Newton box sitting on a table. What is the net force on the bottom box? What is the net force on the top box? Why?

The net force on the bottom box is zero Newtons (because it is in equilibrium). The net force on the top box is also zero Newtons because it is also in equilibrium.

5. A 5 Newton object and a 15 Newton object are both released from rest at the same height. If air resistance is negligible, which object will hit the ground first? Why?

They will hit the ground at the same time. The 5 N object has a smaller force but also a smaller mass than the 15 N object. Since F-net = ma, this means that they will have the same acceleration and hit the ground at the same time.

6. You and a friend are studying forces. Your friend says:
“The gravitational force the Earth pulls on you and the force the floor pushes up on you are Newton’s Thrid Law Force-Pairs. This is because you are at rest so the net force must be zero.” Do you agree with your friend? Why or why not?

I do not agree. Although those forces are equal and opposite, they are not 3rd law pairs. The pairs must be on different objects. The third law pair for the Earth pulling on the person is the person pulling on the Earth.

7. A 5 Newton force is applied to a 10 kg box on a frictionless surface and the box accelerates at 0.5 m/s per second. What would happen if the 5 Newton force was replaced with a 10 Newton force? Explain.

If the force is doubled, then the acceleration would also double since F-net = ma. In this case, the acceleration would be 1 m/s per second.

8. A skydiver jumps off a cliff and falls towards the Earth. At what point during the fall will the skydiver have the greatest acceleration? Why?

The acceleration will be greatest right at the beginning of the fall. At this time, the speed is zero (or very small) and so there is little to no air resistance. This means that the only force on the skydiver is gravity. Later, the net force will be less (and so will the acceleration) because the air resistance will get larger.

9. If I drop a rock and a feather in the room, the rock will hit the ground first. Explain why this happens in terms of forces.

The rock will hit the ground first because it has a greater gravitational force that is much larger than the air resistance on that rock.

10. Suppose a 20 Newton box is falling at terminal speed. What is the air resistance force on this box and what is its acceleration?

The air resistance is 20 N and the acceleration is zero because it is at a constant speed – this means the net force must be zero.

11. Consider a high-speed bus colliding head-on with an innocent bug. Which is greater, the force on the bug or the force on the bus? Why?

The forces are the same. The bug pushes on the buss and the bus pushes on the bug. These are two aspects of the same force – the force between the bug and bus.

12. Calculate the acceleration of that starts from rest and rolls down a ramp and gains a speed of 25 m/s in 5 seconds.

a = 25 m/s / 5 sec = 5 m/s per second.

# Test 1 grades posted

I posted test 1 grades on BlackBoard. A word of caution - there were some issues with blackboard, so consider this your unofficial grade. If you get your test back on Monday and the grade is different, I am going with the grade on the paper.

# Grades for Test 1

I normally don’t post grades on BlackBoard (because BlackBoard hates me) - but in this case, I will. We will not have class for a while (because of Mardi Gras). As soon as I have the tests graded, I will post them.

Also, I will soon post the test key for test 1.

# Stuff for Test 1

Just a couple of quick notes about the first test. It will cover chapters 1 and 2. The main points.

- Aristotle and motion
- Mass and inertia
- Net force - Newton’s second Law (Net Force = mass x acceleration)
- Vectors and Scalar
- Speed vs. Velocity
- The difference between velocity and acceleration
- Friction
- Weight
- Acceleration of a free falling object
- Newton’s third law (forces come in pairs)
- You should be able to identify forces on an object
- You should be able to identify Newton’s third law pairs
- You should be able to describe things that are falling (in terms of Newton’s second law) both with and without air resistance

# Science and "why?"

This is a great video clip of an interview with Richard Feynman. If you are not familiar with Feynman, let me just say that he was a pretty important physicist. He was also interested in helping the general public understand science.

In this short interview, someone asks why magnets work. Here is Feynman’s response:

You may think Feynman is being a jerk. Maybe he is, but that is not his intention. He is trying to explain some of the basic ideas of the nature of science. I will post more on this topic later.

# Force Game

I mentioned in class that I would post this force game. Here it is.

http://phet.colorado.edu/simulations/sims.php?sim=Maze_Game

Some other stuff you might like: Forces in 1-D

Also, here is a force game I made:

Learn more about this project

Click on the applet and then press space to start. The arrow keys act as forces. Try to move the box into the red circle (and stop) there in as short of a time as possible.

# Chapter 3 Lecture

Chapter 3 is a little bit longer than I wanted. So, I broke it into two parts. Part 1 is posted in the lectures page and covers the momentum principle. Part 2 will cover the work-energy principle.

# A note about attendance

Just to be clear.

I take attendance as required by the university. Other than university-related stuff (mostly that deals with financial aid), attendance does nothing.

You are welcome to come to class or not to come to class as you see fit. I hope that you will be in class, but it is important to realize that the lectures are for you. If you find that reading the book is just as good as lecture, that is ok with me.

# Chapter 2 Uploaded

I posted my version of chapter two.

# Chapter 2 Homework

For Chapter 2:

Review Questions:
- 2, 11, 14, 15, 22, 27

Exercises:
- 1, 5, 7, 10, 11, 15, 16, 17, 19, 27

Problems:
- 2, 3, 6, 11

# Other Slides

As I said, I posted the other slides (the powerpoint stuff) on BlackBoard in the documents section.

# Chapter 1 Homework

For chapter 1, I recommend the following:

Review Questions:
- 1, 2, 5, 10, 16, 17, 27

Exercises:
- 1, 3, 7, 12, 15, 20, 22, 26, 27

Problems:
- 1, 2, 5, 9

# Deductive reasoning

Here is the video I was going to show in class.

# Lectures

I have posted the first two lectures. Lets see how this works out, but for now I have posted them as pdf files.

I will try to post the lectures in advance of the actual lectures.

# First Announcement

This is where I will post stuff that I consider to be possibly useful.